If I'm working on something interesting I can do 8, 10, even 12 hours of coding without being aware of the time passing; but that's not the point, we're talking of averages here.

Also, some people in 2 hours can obtain the same results of me doing 8 hours of work - that's about quality, so the "woking-harder" it's not a valid argument: the real problem is "working focused"